1. Field of the Invention
The subject invention relates to polyol compositions which are propylene oxide adducts of toluenediamine. The subject polyol compositions are particularly useful in the preparation of rigid polyurethane foams.
2. Description of the Prior Art
Alkylene oxide adducts of various aromatic amines are well known in the art. It is also known that such adducts can be used in the preparation of polyurethane foams.
Generally alkylene oxide adducts of aromatic amines are prepared by reacting an alkylene oxide with an aromatic amine at temperatures of 90.degree. C. to 125.degree. C. in the presence of an alkoxylation catalyst. These temperatures are preferred in order to avoid side reactions which decrease the yield of the desired product. Moreover, low levels of catalyst (0.2 part or less per 100 parts of amine) are also preferred because this reduces the time and expense needed to remove the catalyst.
It is also known that ethylene oxide adducts of aromatic amines have lower viscosities than corresponding propylene oxide adducts, but that the reactivity profile and compatibility of ethylene oxide adducts make processing of polyurethane foams difficult.
On the other hand, propylene oxide adducts have better reactivity profiles and are compatible with other polyurethane reactants, but they are too viscous unless several moles (20 or more) of propylene oxide are added to the amine. The problem with adding several moles of propylene oxide is that the polyols produced have high equivalent weights which make them unacceptable for the preparation of rigid polyurethane foams.